1. Field of the Invention
The present invention relates to an optical disk apparatus, and more particularly, to optimization of recording conditions employed by an optical disk apparatus capable of recording data.
2. Related Art
According to a known technique, when data are recorded by means of a CD-R/RW drive, a DVD-R/RW drive, or the like, test data are recorded in a test area on an optical disk (e.g., a power calibration area; i.e., a PCA area). Recording power is optimized on the basis of the quality of a signal reproduced from the test data. Such a technique is generally called optimum power control (OPC), and the power optimized through OPC is used in recording data in data areas of an optical disk.
FIG. 6 shows, as an example, a flow chart pertaining to data recording processing to be performed by a DVD-RW drive. First, when a DVD-RW disk is loaded into a drive, a controller provided in the drive performs OPC operation (S101). Specifically, this is performed by sequentially recording test data in PCA areas while laser power is changed in increments of 0.5 mW. For each level of laser power, the quality of a reproduced signal produced by reproduction of the test data is evaluated. A β value, a degree of modulation “m,” a γ value, jitter, or the like is used as the quality of the reproduced signal. For example, when a β value is used as a parameter for evaluating the quality of the reproduced signal, the β value representing the quality of the reproduced signal is compared with a preset target β value, whereby laser power closest to the target β value is extracted. After execution of OPC, the thus-extracted laser power is set to recording power (S102).
After recording power has been set, RMD (recording management data) serving as management data are recorded in an RMA serving as a recording management area of the DVD-RW (S103). After recording of the management data RMD, verification is made as to whether or not the RMD have been recorded without fail (S104). The reason for this is that, if the RMD fail to be read, the DVD-RW cannot be activated; or even if the DVD-RW can be activated, the extent to which data have been recorded becomes unknown because of absence of management data, thereby hindering accurate recording of data. If the result of verification shows that the RMD cannot be read, RMD will again be written or OPC will again be performed in order to optimize recording power and write RMD, thus performing verification. In contrast, if the result of verification is positive; that is, if the RMD can be read, data are recorded in the data areas at the recording power set in S102 (S105).
FIG. 7 shows a data format of the DVD-RW. A PCA (power calibration area), an RMA (recording management area), a lead-in area, and data areas are present on the DVD-RW. An RMA lead-in and RMD are recorded in the RMA. The RMA lead-in includes an ID of a drive manufacturer, a serial number, a disk ID, or the like. Further, the RMD include OPC-related information, data area information, recording mode information, or the like. The RMD are made up of 28 sets of data ranging from set 1 to set 28. Each set includes five blocks. Each block includes a concatenation loss area and Fields 0 to 14. Each block has a size of 32 KB. Different information items are recorded in the Fields 0 to 14 in accordance with the mode of the DVD-RW (i.e., an incremental mode, a disk-at-once mode, or an overwrite mode). For instance, in an incremental mode (which is a write-once mode, and data can be sequentially recorded; when recording of data has been completed, information about completion of the data is recorded in the RMA), common information is recorded in Field 0; OPC information and information about a pointer of an RMD set are recorded in Field 1; and data designated by the user and erasing operation information are recorded in Field 2. The erasing operation information shows an erasing position and the number of times erasing operation has been performed.
If the RMD serving as management data can be verified and read, data supplied from a higher-level apparatus are recorded in data areas. If a record margin is small, there will arise a case where, even if RMD can be read, data cannot be read after having been actually recorded in the data areas. The reason for this is that during the verification operation for the RMD verification is made solely as to whether or not RMD can be read; the recording quality of the data are not quantitatively evaluated. The quality of the data recorded in the data areas is not ensured. Particularly, a wide variety of optical disks are circulated in the market, and variations exist in a characteristic of a recording film. There often arises a case where, even when an attempt is made to reproduce data recorded by a certain drive through use of another drive, the attempt ends in a failure because recording power is not always optimal.
In order to prevent occurrence of such a failure, there have been proposed a techniques for ensuring recording quality by further optimizing recording power obtained through OPC. For instance, according to one technique, a CD-RW drive records data in data areas at the recording power obtained through OPC and detects errors by reproducing the data. When the errors exceed an allowable value, OPC is again performed, thereby optimizing recording power. The data written in the data area are overwritten at the thus-obtained recording power. Alternatively, according to another technique, when OPC is performed in the test area, the quality of a signal reproduced from the test data is recorded, along with errors in the signal, whereby recording laser power is set to laser power at which the errors are reduced to an allowable value or less. Please refer to the following publications for the above-described techniques.
Japanese Patent Laid-Open Publication No. Hei 11-45440
Japanese Patent Laid-Open Publication No. 2002-260230
However, in the case of a configuration in which data are recorded in data areas and errors in the data are detected, to thereby again perform OPC, data are written in data areas for a trial, thereby presenting a problem of consumption of data areas. The data written in the data areas for a trial must be overwritten. In principle, the technique is limited to a CD-RW disk or the like. Another problem is that the technique cannot be applied to a disk which does not enable overwriting of data. Even in the case of a configuration in which test data are recorded in a test area (i.e., a PCA) and errors in the test data are detected, extra test data must be recorded for detecting errors (at least test data corresponding to 16 sectors which are equal to one ECC block, and test data of at least this quantity must be recorded for each of a plurality of laser power levels), thus consuming the test area. Further, a time required to perform OPC is a wait time for the user during which data are not recorded. In view of convenience, an increase in the time required to record test data is not preferable.